The present invention relates in general to the compact integration of circuit modules in a chassis, and more particularly to a technique for providing a high density interconnection between multi-pin circuit modules, by way of a high density conductor chassis backplane.
Constant efforts are directed toward the miniaturization of electrical circuits and components to thereby increase the circuit density per unit area. The integrated circuit technology has made significant advances in the development of the semiconductor layout, masking equipment, steppers, etc., to thereby form a greater number of transistor circuits onto a smaller area of the semiconductor material. Further, the miniaturization of components and the hybridization thereof into encapsulated modules is an ongoing endeavor toward the miniaturization of electrical circuits. Advantage is taken of the smaller size of the components, encapsulated modules, integrated circuits, etc., by allowing many more of such components to be interconnected on a printed circuit board. Indeed, printed circuit boards themselves have multiple layers of conductors, as well as high density conductors to thereby facilitate the interconnection of the many components mounted thereto.
Notwithstanding the ongoing miniaturization of components, such components are still required to be interconnected together not only by way of the printed circuit boards noted above, but such printed circuit boards, or modules, are also often interconnected together in a chassis. A common technique for housing a number of printed circuit modules is to provide metallic contacts on one or both opposing edge surfaces of the printed circuit board, and a corresponding female connector mounted in the chassis. In this manner, when the printed circuit board is inserted into the chassis by way of guide rails, the edge conductors automatically mate with corresponding connector contacts. Moreover, the connectors are interconnected with other connectors by wires that are often manually or automatically wound around terminals extending from the connector. Instead of the hard wired interconnections between chassis connectors, a multi-layer backplanes are often utilized to provide the interconnections between the connectors. In this instance, the connector terminals are soldered into the backplane conductors. Although this printed circuit board backplane is relatively expensive, it reduces the time required to assemble a complete chassis and connector interconnections.
While the foregoing chassis assembly functions very well for its intended purpose, a problem arises when it is desired to increase the number of connections between the printed circuit modules and the connectors. One approach has been to simply extend the length of the printed circuit board edge to accommodate more contacts, but this solution requires a larger connector and chassis. Another technique is to mount a separate, small printed wire board to the printed circuit board, but spaced therefrom, with wiring interconnecting the two, so that a pair of edge connectors can be utilized for the circuit module. Yet another approach has simply been to reduce the size and spacing between the edge contacts of a printed circuit board, thereby increasing the density of the contacts. This technique can be utilized to the extent that the contact surface area is reduced until inadequate metallic contact area exists to carry the requisite electric current.
While the utilization of printed circuit boards with components soldered thereto has experienced a significant success, inherent disadvantages still exist. For example, the components extending from the printed circuit board are subject to damage especially when stacked or inventoried together, without packing material therebetween. Further, the physical handling of such circuit boards when inserting or removing the same from the chassis, subjects the exposed components to damage or short circuiting with other components.
It can be seen from the foregoing that a need exists for an improved printed circuit module design that provides protection to the components thereof from the environment, as well as provides a high degree of interconnectivity to a backplane. A further need exists for a technique to provide self-alignment of high density pins/sockets between a printed circuit module and a backplane to thereby prevent bending or misalignment of the respective pins and sockets. Yet another need exists for an interconnection technique between a high density socket of the printed circuit module, and a corresponding high density pin arrangement of a backplane, while yet maintaining the assembly procedure relatively uncomplicated and maintaining a high degree of reliability.
In accordance with the principles and concepts of the present invention, there is disclosed a chassis assembly that provides a high degree of interconnectability between the printed circuit modules by way of a high density conductor backplane. In accordance with other aspects of the invention, the printed circuit modules are enclosed so as to protect the components from physical damage, while yet allowing easy accessability to the components when adjustment or repair is required. Further, the particular sliding engagement employed between the printed circuit modules and the chassis guide rails provide a high degree of alignment between the high density pins and sockets.
In accordance with the preferred embodiment of the invention, a module case provides physical protection to one or more printed circuit boards housed therein. Each printed circuit board has a back edge thereof with miniature socket contacts soldered to corresponding pads on each side thereof, thereby providing a high density of interconnections to corresponding miniature pin contacts in a chassis backplane. The socket members of each printed circuit board are maintained aligned and housed within an insulator board to thereby prevent physical damage or misalignment of the individual sockets. The protective case of each multi-board module is preferably formed of a metallic material to provide a high degree of heat transfer from the module to the chassis via the guide rails. Further, each protective case is formed so as to have one vertical metallic side thereof removable, thereby exposing the components for repair or adjustment. The side cover of the case is removably attached by way of a snap-lock arrangement. A faceplate portion of the case includes a hinged pull-tab to allow easy removal of the module from the chassis. The module is retained in the chassis by way of the sliding friction contact between the miniature pins and sockets.
The protective case that houses one or more printed circuit boards, or other types of electronic assemblies, is preferably pocket-sized for easy transporting of the same. Further, each case does not have four right angle corners for sliding into the chassis rails, but rather has beveled or chamfered corner edges, each of which engages by way of a small-area rounded guide edge of the chassis. In this manner, the module is aligned or registered by way of these four contact surfaces to thereby provide a high degree of alignment between the module socket contacts and the backplane pin contacts. Further, the sliding surfaces are anodized to facilitate the sliding action between the module case and the chassis guide rails.
According to another feature of the invention, the chassis is provided with a number of module openings which need not accommodate a module but rather may have snap fit therein a blank faceplate. The blank faceplate provides a decorative cover to an unused slot opening, and prevents dust and particles from easily entering the chassis. Another feature of the invention is that the blank faceplate can be constructed with a hinged cover member fastened to the back side thereof, and spring loaded so that when the blank faceplate is snap locked into the slot opening, the hinged cover pivots internal to the chassis to provide a cover to an adjacent slot opening. When the adjacent slot has inserted therein a module case, the spring loaded cover is pivoted out of the path of the module as it is inserted into the adjacent slot opening. When the module case is removed, the hinged cover returns to a position in which the slot opening is covered.